Bio-organic manure and minerals synergically revitalize soil quality via aggregation and pore structure in saline soils

Abstract

Soil salinization may deteriorate soil structure and soil quality, particularly in coastal regions. However, the impact of organic and inorganic amendments on soil aggregation, pore structure and their correlation with soil quality remains unclear. Herein, we examined the changes in aggregate-size distribution, the associated cementing agents, and pore structure identified using X-ray computed tomography in the Yellow River Delta, North China. Soil samples were collected from the 0- to 20-cm layer and treated with non-amended control (CK), formulated Fe-Si/Ca-based material containing wollastonite and iron mining tailings (FeSi), bio-organic manure (BOM), and a combination of BOM with FeSi (FeSi + BOM). The results showed that BOM and FeSi + BOM markedly boosted soil macroaggregates by 3.0–5.0 times and structural stability, reflected by mean weight diameter (41.9%–57.0%), in comparison to CK. This improvement may likely be due to the increased organic binding agents (e.g., soil organic carbon, dissolved organic carbon, and total glomalin-related soil proteins) and ions like Ca²⁺ and Mg²⁺. The utilization of BOM and FeSi + BOM enhanced the 3D pore structure and functions. This enhancement was evidenced by the increased image-identified porosity (by 53.3%–77.3%), pore connectivity (by 1.9–3.2 times), optimized pore-size distribution (e.g., 100–500 µm and >500 µm), and increased saturated hydraulic conductivity (4.4–6.8 times). Collectively, BOM, either alone or in combination with inorganic ameliorations, has the potential to enhance soil quality significantly, providing effective strategies for rehabilitating saline soils.